Glass plate manufacturing comprises three principal steps, melting of the raw material to form a molten glass, forming the molten glass into sheets or plates and finally processing the plate into a final shape satisfactory to purchaser or user. Methods of forming thin glass plates include an overflow downdraw process, or fusion process, wherein a molten glass is supplied to an open-top conduit. The molten glass overflows the conduit and flows down converging surfaces comprising the outer surface of the conduit. At the bottom of the conduit the separate flows rejoin, or fuse, to form a thin glass ribbon. Other methods include the well known float process, where molten glass is floated on a bath of usually tin, slot draw, up draw and others. Generally, all of these processes include a final processing step of separating individual plates of glass from a parent sheet, sizing the plates in a cutting operation and edging the glass to strengthen the piece for subsequent handling operations. The individual plates are edged both to remove flaws that may be formed when individual plates are cut from the parent, and to eliminate sharp edges that are easily damaged during handling.
Thin plate glass edging is typically done using a grinding wheel consisting of formed grooves. These formed grooves will create a shape on the glass that mirrors the groove. An example of this process is documented in U.S. Pat. No. 6,685,541 to Brown, et al. and U.S. Pat. No. 6,325,704 Brown, et al.
As the need for ever thinner plates of glass increases, owing largely to the electronic display industries (computers, cell phones, digital cameras and the like), producing a consistent edge shape in the wheel is becoming increasingly difficult:
the wheel profile becomes misshapen with use, causing inconsistent plate edge shape;
the surface area used by the wheel is limited to the groove, which increases the cost due to poor utilization of material;
the relatively small surface area of the wheel actually contacting the glass necessitates the use of coarser abrasive grain sizes and, ultimately, poorer glass sheet surface finishes;
the lack of chip clearance between the glass and the wheel during grinding increases the potential for defects in the plate as the wheel becomes clogged by glass particles; and
wheel profiles are difficult to make when a small tight radius is required. Formed wheels are typically made using an EDM process. As the tool used to create the form wears, often quickly, it creates an undesirable blunt profile at the bottom of the resultant groove.
The edging process generates particulate (e.g. chips), which is often difficult to remove from the plates.